Scientists in Britain first became aware of Bovine Spongiform Encephalopathy (BSE) in November 1986 with the appearance in cattle of a newly-recognised form of neurological disease.

Up to the end of January 1998, approximately 170,000 cases of the disease were confirmed in the UK.

At least 100,000 more cattle were culled in an attempt to stop the spread of the disease.

BSE was dubbed Mad Cow Disease after pictures were shown of disoriented, brain-damaged cattle collapsing in their pens.

Scientists became aware of the sponge-like nature of the disease in 1986

Studies suggested that the source of disease was cattle feed prepared from carcasses of dead cattle, and that changes in the process of preparing cattle feed introduced in 1981-1982 may have been a risk factor.

BSE affects the brain and spinal cord of cattle and is characterised by sponge-like changes visible with a microscope.

It is highly stable and resists heating to normal cooking temperatures and even higher temperatures such as those used for sterilisation, freezing, and drying. The disease is fatal for cattle within weeks of symptoms appearing.

BSE is one of several different forms of transmissible brain disease which affect animals. Others include scrapie, a disease common in sheep, and a similar disease in animals such as deer.

Scientists are researching links between BSE and Creutzfeldt-Jakob disease (CJD) a brain disease which occurs in humans.

Twenty-three people have died of a new variant of CJD which is thought to have strong links with BSE.